1. Field of the Invention
This invention relates generally to semiconductor integrated circuit devices having high speed semiconductor logic elements therein.
2. Description of the Prior Art
Recently, with the development of compound semiconductor elements, high speed logic operations have become used in semiconductor integrated circuits. In particular, GaAs logic integrated circuits using field effect transistors on a GaAs substrate are common.
However, the excellent high speed performance of a GaAs integrated circuit chip itself is harmed if the GaAs chip is packed within the same package used for silicon integrated circuits. Namely, sharp transient current flows in the power supply line when inner logic elements switch at high speeds causing a power supply voltage drop due to the inductance of the power supply lines. For example, if the transient current flowing in the power supply lines during the switching time of 100 psec is 10 mA and the inductance of the power supply lines in the package is 2 nH, power supply voltage drops become about 2 mV
This power supply voltage disturbance will unstabilize the operation of inner logic elements. Since the noise margins of the logic element using the GaAs MESFET are very small, the minute disturbance of the power supply voltage prevents normal operation. Therefore, the high speed switching operation will be difficult.
In conventional low speed integrated circuits, the above-mentioned power supply voltage disturbance has been disolved by of a connection the de-coupling condensor between the power supply line and the ground line outside of the package. However, in high speed circuits, e.g., in the GaAs logic integrated circuit, the effect of the inductance of the power supply line inside the package is not compensated for by a capacitor connected outside of the package.
There are others reasons it is difficult to pack the GaAs logic integrated circuit into the conventional package of a low speed integrated circuit. For example, the reflection of the high frequency signal due to the unmatching of the characteristic impedance of the wirings within the package, the crosstalk between signal wirings within the package, and the unmatching of characteristic impedances between the wiring within the package and microstrip line on a printed circuit in assembling the GaAs logic integrated circuit on the printed circuit.